Technical Abstract:
Use of soil bacteria to selectively suppress grass weeds is a promising alternative control method that may decrease the need for tillage to reduce weed seed populations. Microorganisms can be used to deliver to the seed the natural inhibitory compounds they produce. We followed the survival of introduced bacteria in soil and on roots. Fall introduced bacteria declined in the soil to near or below detection during the winter, but increased in the spring. The bacteria colonized roots during the fall, winter, and spring then declined with summer. Even though the bacteria in the soil declined to below detection, a sufficient population was present to colonize the root. We also investigated the use of delivery systems and reduced herbicide application. When encapsulated in various formulations, bacterial survival increased 20 to 40% and biocontrol efficacy increased from 30 to 90%. Bacteria plus low levels of certain herbicides showed an additive effect on weed suppression. The goal of our research is to develop strategies to effectively utilize microorganisms in the control of grass weeds.